Process for producing a magnetic read write head and head obtained by this process

ABSTRACT

A first magnetic material film is deposited on a support, a groove is etched in the first magnetic film which is shaped like a figure eight, a double coil is formed and is wound respectively around the two central pole pieces. An insulating material layer is deposited and etched in step form, the step having a side facing the central channel. An .[.magnetic.]. .Iadd.amagnetic .Iaddend.film is deposited on the thus etched step, and the film is etched so as to only leave a wall perpendicular to the plane of the films. This is followed by the deposition of a magnetic film and then a protective layer, the assembly being divided off so as to expose two pole pieces separated by an .[.air gap.]. .Iadd.amagnetic gap.Iaddend..

BACKGROUND OF THE INVENTION

The present invention relates to a process for producing a magnetic readand write head and to a head obtained by this process. It is used inmagnetic recording equipment and in particular in computer memories.

The magnetic head according to the invention is of the type comprisingtwo pole pieces, a double flat spiral coil surrounding each of the polepieces and an air gap filled with an amagnetic material, the latterbeing flush with the level of the planar surface forming what is calledthe flight or displacement plane of the head. The magnetic recordingsupport moves relative to the head in front of the air gap and parallelto the displacement plane. During writing, a current flowing in thewinding leads to a magnetic field at the air gap, so that information iswritten into the support. Conversely, magnetic information written on tothe moving support induces a field in the pole pieces, i.e. a current inthe coil and a voltage at the terminals thereof, which constitutes ameasuring signal. As the magnetic field involved in these reading andwriting operations is parallel to the recording support, the termhorizontal magnetic recording is sometimes used.

For example, such a head is described in Japanese Pat. No. 56 83823filed by FIJITSU K.K. and entitled "Production of horizontal thin filmmagnetic head", whose abstract was published in Patent Abstracts ofJapan, vol. 5, no. 150 (P-81) (822) of 22.9.1981.

The process for producing such a head comprises the end to end bondingof two thin magnetic pieces on a substrate, said magnetic pieces beingseparated by a nonmagnetic layer defining the air gap. This assembly isthen machined to reduce the height of the air gap. Separately a supportis formed comprising a double winding surrounding the two pole pieces.These two subassemblies are then bonded together.

Such a process suffers from numerous disadvantages. Firstly, it requiressensitive fitting of small parts, which makes it relatively incompatiblewith industrial, automated processes. The read and write pole pieceshave on the one hand a significant width, which is prejudicial to theefficiency of the head, and on the other hand is of a relativelynon-reproducible nature, which leads to performance variations. Finally,it can induce interference fields in the recording layer.

SUMMARY OF THE INVENTION

The present invention relates to a process for producing a magnetic headobviating the aforementioned disadvantages. As operations based on thinfilm technology are used, the process is suitable for automation. Thewidth of the read and write pole pieces defined by the thickness of athin film, so that said thickness is limited and perfectly reproducible.Moreover, the conductor winding is inserted between two magnetic filmsand is consequently completely shielded.

The present invention more specifically relates to a process forproducing a magnetic read-write head, wherein it comprises theoperations of depositing a first magnetic material film on a support,etching a groove in said first magnetic film, said groove being shapedlike a figure of eight with two loops having in common a rectilinearcentral portion, the magnetic film being preserved within said two loopsand forms there two central pole pieces separated by a central channelcorresponding to the central part of the figure of eight, filling thegroove with an electrically insulating material, etching in theinsulating material a notch forming a double groove wound respectivelyaround the two central pole pieces, depositing a conductive coating atthe bottom of the double groove and filling the double groove with anelectrically insulating material, depositing an insulating materiallayer, etching in said layer a step having a side facing the centralchannel, but which is slightly offcentred with respect thereto,depositing an amagnetic material film on the thus etched step, etchingsaid amagnetic film so as to only leave a wall perpendicular to theplane of the films and constituted by that part of the amagnetic filmdeposited on the side of the step depositing a second magnetic materialfilm forming a boss covering the wall, depositing a protective coatingexactly following the shape of the boss and cutting the protectivecoating of the boss and the amagnetic wall, so that two pole piecesseparated by an .[.air.]. .Iadd.amagnetic .Iaddend.gap appear.

The present invention also relates to a magnetic head obtained by theprocess defined hereinbefore. The head is characterized by the presenceof two magnetic coatings, which completely secure between them thespiral coil and in that the read and write pole pieces are constitutedby sections of a thin magnetic film.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in greater detail hereinafter relative tonon-limitative embodiments and the attached drawings, wherein show:

FIGS. 1 to 8 various stages of the process according to the invention.

FIG. 9 in section, the head according to the invention.

FIG. 10 an exploded view of the head according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1 support 20 can be made from a ceramic material, a dielectricmaterial, or in the form of a silicon wafer similar to that used insemiconductor technology. In this case, the wafer is coated with asilica coating 22 formed by thermal oxidation. A film 24 is thendeposited from a high permeability, strong magnetization magneticmaterial, such as a ferrite, or an alloy of FeNi or Co, Zr, Nb. Thethickness of the magnetic coating is between 0.5 and 5 μm.

FIGS. 2 and 3 show a groove 26 in the form of a figure of eight etchedin the film 24. The etching of the groove leaves behind two central polepieces 26a, 26b separated by a central rectilinear channel 26c. Groove26 is obtained with the aid of a resin mask produced by photolithographyand etched either chemically, or by dry etching.

The etching depth of groove 26 corresponds to a fraction of thethickness of film 24 (a third or a half).

FIG. 4 shows the filling of groove 26 with a dielectric material 27,such as silica or resin. A well known planarization operation ensuresthat the dielectric is only located in the groove and not on the surfaceof film 24.

A double spiral groove 28 and 30 is then formed in the fillingdielectric 27 (FIG. 4). This is followed by the deposition of anelectrically conductive material layer 31 at the bottom of the doublegroove. This material can be copper or aluminium. This is followed bythe formation of a coil, whose plane is parallel to the recording layer.The coil comprises a half 28 surrounding the pole piece 26a and a half30 surrounding the pole piece 26b.

The exploded view of FIG. 9 more clearly shows the configuration of thiscoil. It can more particularly be seen that the width of the conductorin the central part of the coil is smaller than in the two lateralparts, so that there is a high current density in the first part, whichcontributes to a greater efficiency of the head. The two grooves 28 and30 are then filled with an insulating material identical or similar tomaterial 27.

A dielectric layer 32 is then deposited on the assembly and ispreferably constituted by a photosensitive resin. Its thickness isbetween 0.5 μm and a few microns. A step is formed by photolithographyand its side 33 is displaced with respect to the central channel 26cseparating poles 26a and 26b. This displacement is approximately equalto half the thickness of the amagnetic film 34, which is then deposited.This amagnetic film is advantageously of silica or alumina and coversthe resin step, as shown in FIG. 7.

By anisotropic reactive ionic etching and following dissolving of theresin, a vertical wall 34a is left, whose thickness is equal to orslightly less than that of the amagnetic film 34 and whose height isequal to or less than the thickness of the resin layer 32.

This is followed by the deposition of a magnetic film 36, which can beof the same nature as film 24. Film 36 forms a boss at wall 34a, as canbe seen in FIG. 8. This is followed by the deposition on the assembly ofa hard insulating protective coating 38, which can be of silica oralumina and exactly follows the shape of boss 37.

Finally, a resin layer 40 is deposited and will provisionally serve todivide off the bosses and wall 34a, dividing off taking place in coating38.

The top of wall 34a is then exposed forming an .[.air.]. .Iadd.amagnetic.Iaddend.gap between the two pole pieces 36a, 36b. The magnetic film 36has a thickness between 0.2 and 1.5 μm, i.e. it is very thin. The sameapplies with regards to pole pieces 36a, 36b, whose width is of the sameorder of magnitude as said thickness. This leads to the high efficiencyof the magnetic head according to the invention.

FIG. 9 shows the head which is finally obtained. The arrows representingthe flux or flow lines on writing in a magnetic support 42 moving infront of the flight or displacement plane 41 constituted by what is leftof the coating 38.

It is pointed out that the two lateral portions of the coil aremagnetically shielded by the two films 24 and 36, so that they produceno leakage field towards the recording coating 42.

Finally, FIG. 10 shows an exploded view of the head observed in front ofits flight or displacement plane. Only the ends of the two read andwrite pole pieces 36a, 36b separated by wall 34a are flush with thelevel of the flight plane.

What is claimed is:
 1. A process for producing a magnetic read-writehead, comprising the steps of: depositing a first magnetic material filmon a support, etching a groove in said first magnetic film, said groovebeing shaped like a figure eight with two loops having in common arectilinear central portion, the magnetic film being preserved withinsaid two loops and forms there two central pole pieces separated by acentral channel corresponding to the central portion of the figureeight, filling the groove with an electrically insulating material,etching in the insulating material a notch forming a double groove woundrespectively around the two central pole pieces, depositing a conductivecoating at the bottom of the double groove and then filling the doublegroove with a first electrically insulating material, depositing asecond insulating material layer on the two central pole pieces and onthe first electrically insulating material, etching in said layer a stephaving a side substantially perpendicular to the surface of the centralportion of the figure eight but which is slightly off-center withrespect thereto, depositing an amagnetic material film on the thusetched step, anisotropic etching said amagnetic film so as to only leavea wall of said amagnetic film perpendicular to the plane of the filmsand constituted by that part of the amagnetic film depositing on theside of the step, depositing a second magnetic material film forming aboss covering the wall, depositing a protective coating on said secondmagnetic material film and covering the boss and cutting the protectivecoating of the second magnetic material film and the amagnetic wall,along a common horizontal plane substantially parallel to said firstmagnetic film, pole pieces are separated by an .[.air.]. .Iadd.amagnetic.Iaddend.gap.
 2. A process according to claim 1, wherein the support onwhich is deposited the first magnetic material film comprises aninsulating support covered with a dielectric material coating.
 3. Aprocess according to claim 1, wherein the thickness of the secondmagnetic material film is between 0.2 and 1.5 μm.
 4. A process accordingto claim 1, wherein the second insulating material is a photosensitiveresin, which can be removed by dissolving.